Passive infrared sensors (PIRs) are electronic sensors that measure infrared (IR) light radiating from any objects within a field of view of the PIR sensor. All objects emit heat energy in the form of radiation. This emitted radiation is in the infrared region, with longer wavelengths than those of visible light, typically in the region of 700 nm to 1 mm.
PIR sensors are passive in that such sensors do not radiate any energy for the purpose of detection. Rather, PIR sensors detect energy radiated from other objects.
Existing PIR sensors may be utilised in monitoring devices, such as motion detectors, and are sometimes referred to as passive infrared detectors (PIDs). Such motion detectors are commonly used for burglar alarms and automatically-activated lighting systems. As such, these motion detectors are adapted for use in indoor environments or under protected eaves, where simple housings are adequate. Further, such applications have well-defined fields of view, as the motion detectors can be positioned to cover a known entrance or exit.
Existing PIR motion sensors are not suitable for outdoor environments with little or no protection from the weather. Accordingly, water ingress may cause intermittent faults, damage to circuitry, and even complete failure of such devices. Further, existing PIR devices are susceptible to malicious damage or tampering.
Thus, a need exists to provide an improved monitoring device.